The products of translation of the dsRNA species of killer, neutral and sensitive strains of yeast will be compared with the polypeptides comprising virus-like particles and extracellular toxin produced by these strains. Evidence for a cell-bound toxin precursor and an associated immunity factor will be sought. Transcripts of the dsRNA's will be characterized in polysomal RNA. The segregation of the sensitive or neutral phenotype from a particular unstable killer strain will be investigated.